Horizontal compression type automatic filter press

ABSTRACT

A horizontal compression type automatic filter press for filtering and squeezing slurry through an endless filter cloth, comprises filter plate open and close means for opening and closing all of filter plates simultaneously, diaphragms each having a main portion, which is secured to a movable filter plate, being thicker than the periphery of the diaphragm secured to a stationary filter plate, double surface filter plates each providing a filtration resistance difference between opposite surfaces thereof, filter cloth transfer means having two sets of rollers arranged one above the other, the diameter of the one set of rollers above arranged being smaller than that of the other set of rollers. The filter press according to the invention accomplishes minimization of water content of filter cakes obtained by the press and remarkably high average filtering rates and achieves full automatic operation and shortening of the overall length of the press.

United States Patent 151 3,696,930 Tokura 14 1 Oct. 10, 1972 [541HORIZONTAL COMPRESSION TYPE 447,551 l/ 1913 France ..210/226 [72]Inventor: Tadao Tokura, Handa City, Japan [73] Assignee: NGK Insulators,Ltd., Nagoya City,

Japan [22] Filed: Dec. 9, 1970 [21] Appl. No.: 96,545

[30] Foreign Application Priority Data April 4, 1970 Japan ..45/28271[52] US. Cl ..210/225 [51] Int. Cl. ..B0ld 25/32 [58] Field of Search100/198; 210/224-231 [5 6] References Cited UNITED STATES PATENTS1,404,490 1/ 1922 Stevenson..... ..100/ 198 X 3,098,429 7/1963l-lagglunn ..210/226 3,121,681 2/1964 Baxter ..210/104 3,153,630 10/1964Green ..210/230 3,561,600 2/1971 Kunta ..210/225 F ORElGN PATENTS ORAPPLICATIONS 500,069 12/1950 Belgium 210/224 AUTOMATIC FILTER PRESSPrimary Examiner-Reuben Friedman Assistant Examiner-T. A. GrangerAttorney-George F. Dvorak, Stephen T. Skrydlak and Marden S. GordonABSTRACT A horizontal compression type automatic filter press forfiltering and squeezing slurry through an endless filter cloth,comprises filter plate open and close means for opening and closing allof filter plates simultaneously, diaphragms each having a main portion,which is secured to a movable filter plate, being thicker than theperiphery of the diaphragm secured to a stationary filter plate, doublesurface filter plates each providing a filtration resistance differencebetween opposite surfaces thereof, filter cloth transfer means havingtwo sets of rollers arranged one above the other, the diameter of theone set of rollers above arranged being smaller than that of the otherset of rollers. The filter press according to the invention accomplishes minimization of water content of filter cakes obtained bythe' press and remarkably high average filtering rates and achieves fullautomatic operation and shortening of the overall length of the press.

8 Claims, 10 Drawing Figures PATENTEDUBT 1 I912 3 696, 930

SHEEI 1 [IF 4 PATENTEDncI 10 m2 SHEET 3 OF 4 PATENTED BT 10 1912 3.6 96;930

SHEU U [1F 4 HORIZONTAL COMPRESSION TYPE AUTOMATIC FILTER PRESSBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to a horizontal compression type automatic filterpress for compression filtering and squeeze dewatering slurry through anendless filter cloth, and more particularly to filter plate open andclose means for opening and closing all of filter plates simultaneouslyin order to shorten waste time from a termination of one filteringoperation and to a commencement of next filtering operation to performmore effective filtration, a diaphragm for filter plates arrangedbetween a filter chamber and a pres sure fluid chamber, a filter platehaving construction adapted to retain a cake on a portion of the filtercloth on one side of the filter chamber when the filter plates areopened to dislodge the cake accumulated in the filter chamber, andfilter cloth transfer means having less travelling resistance of thefilter cloth.

2. Description of the Prior Art In filter presses hitherto used, watercontents of filter cakes could not be lowered to a valve less than acertain limitation, so that in order to obtain cakes having much lesswater content the cakes must again be squeezed in separate process, orbe subjected to drying process and the like for more dewatering. Toeliminate such an extra process, vertical compression type automaticfilter presses performing continuous dewatering and squeezing in singleapparatus have been suggested. In this type, however, after filterplates have been opened, upon lateral movement of filter cakes, a filtercloth is likely to be broken owing to the weight of cakes acting uponthe cloth and undue powers are required for the movements of the cloth.Horizontal type filter presses having endless filter cloths have beensuggested, which are provided with cake discharging means by which cakesare moved from filter frames taken out from the press after onefiltering operation. With such a construction, however, there aredisadvantages that it requires much time for the movements of the filterframes, thus increasing waste time and decreasing its filtration facultyand that it may be expensive for the discharging means and transfermeans for the filter frames.

In filter plate open and close mechanisms of filter presses hithertoused, there have been three types, that is l) movable block type whereinmovable blocks driven by chains are provided with pawls adapted to beraised by a cam mechanism, by means of which lugs on opposite outersides of filter plates are urged to open or close the filter plates, (2)link type wherein links movable within determined distances are providedon opposite outer sides of filter plates, the links serving to move thefilter plates in synchronism with links on a movable pedestal, and (3)chain type wherein the same operation as in the above link type iscarried out by chains.

In any of these prior filter plate open and close mechanisms, filterplates are opened or closed one by one so that it requires considerableperiod of time. Accordingly, it is desired to improve its filtrationefficiency by shortening the filtering time by the use of thin cakelayers and to improve an average filtering rate by the continuousoperation of the filter press resulting from the minimum waste time byvirtue of a repetition of the short period cycle.

Moreover, diaphragms for filter plates used in compression type filterpresses hitherto used are usually elastic membranes made of rubber andthe like having a uniform thickness, of which mounting to a stationaryfilter plate is effected at the periphery by means of clamp boltstightening the diaphragm and the plate with washers.

In such a diaphragm having uniform thickness, however, owing to the samethickness of the main portion as that of the periphery of the diaphragm,a dimension of the interior of a chamber of the stationary filter plateenclosing a movable filter plate and the diaphragm could not be madelarger than a valve approximate to the total thickness of the movableplate and the main portion of the diaphragm so that a distance of a movement of the movable filter plate caused by fluid under pressure forcedin the pressure fluid chamber is naturally limited, thus adverselyaffecting the high pressure squeeze in the filtering chamber and furtherthe mounting of the diaphragm is complicated and troublesome.

Moreover, in double surface filtration using an endless filter cloth, itis required to retain a cake attached to the portion of a filter clothon either one determined side in order to facilitate removing the cakeafter a filtration has been completed. There have been no filter pressesenabling this problem to be solved.

Furthermore, in a horizontal type filter press having an endless filtercloth hitherto used, rollers arranged a]- temately above and belowfilter frames and filter plates have the same diameter. With such aconstruction, travelling resistances of the cloth may unduely increase,causing an inconvenience in operation.

SUMMARY OF THE INVENTION A primary object of the invention is,therefore, to provide a horizontal compression type automatic filterpress which eliminates manual operation to facilitate its operation andcan obtain filter cakes having considerably low water contents.

A further object of the invention is to provide a filter press providedwith novel simultaneous filter plate open and close means to improve itsaverage filtering rates to much higher values.

An another object of the invention is to provide a filter press providedwith diaphragms of which main portions are thicker than peripheries,thereby obtaining filter cakes having low water contents.

A further object of the invention is to provide a filter press providedwith filter plates adapted to retain cakes on determined sides of acloth, thereby preventing the cakes from being carried along between thecloth and rollers.

A still further object of the invention is to provide a filter pressadapted to mitigate travelling resistances of a filter cloth withoutincreasing the overall length of the press.

BRIEF DESCRIPTION OF THE DRAWING The foregoing objects and other objectsas well as the characteristic features of the invention will become moreapparent and more readily understandable by the following descriptionand the appended claims when read in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an elevational view of an embodiment of a filter press in aclosed position during filtering and squeezing operations according tothe invention;

FIG. 2 is an elevational view of the filter press in FIG. 1, but shownin an opened position;

FIG. 3 is a detailed sectional view of a part of the filter plateassembly of the filter press shown in FIG. 1;

FIG. 4a is a diagrammatical explanatory view of an embodiment of filterplate open and close means of the filter press according to theinvention;

FIG. 4b is a detailed partial sectional view of the portion encircled inline a in FIG. 4a;

FIG. 5a is a graph showing a relation between filtering time and rate inprior art;

FIG. 5b is a graph showing relation between filtering time and rateimproving an average filtering rate according to the invention;

FIG. 6a is a partial sectional view of one embodiment of a filter plateaccording to the invention;

FIG. 6b is a partial sectional view of another embodiment of the filterplate; and

FIG. 7 is a schematic illustration of endless filter cloth transfermeans according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 3, thefilter press according to the invention includes a frame having a sidebar 1 on which aremounted movable filter plates 3 adapted to be clampedby means of a cylinder 2 for clamping the filter plates and stationaryfilter plates 4 enclosing respective diaphragms 15, between which plates4 filter frames 5 are arranged. An endless filter cloth 6 extends aroundtwo sets of transfer rollers R and R these sets of rollers having adifferent diameters and arranged in upper and lower portions of thepress frame in opposition to each other as shown in FIG. 3. The filterpress further comprises a filter cloth drive means 7 with a serpentinemovement preventing unit 13 for the filter cloth mounted on a top frameof the press as shown in FIG. 1, a filter cloth tension unit 8 at thelower end of the press on the same side as the drive means 7, a clothcleaning unit 16 at a location where the endless cloth leaves the mostend filter plate 4, and scraper plates 17 for scraping filter cakes eachat an appropriate location where the cloth 6 is about to ride on thelarger diameter roller R (FIGS. 2 and 3). I

The automatic filter press according to the invention furthermorecomprises a slurry inlet 9, a filtrate outlet 10, a feed blow inlet 11,a back blow inlet 12 and pressure fluid inlet 14. I

The operation of the automatic filter press according to the inventionwill be explained hereinafter. As shown in FIGS. 1 and 2, the slurryintroduced under pressure through the inlet 9 by means of a pump iscompressed to a determined pressure to filter it through the filtercloth 6, after which a valve at the inlet 9 is closed and then waterunder pressure or compressed air is supplied through the pressure fluidinlet 14 to urge the diaphragms 15 against the respective movable filterplates to effect a squeezing operation for a determined period of time.After the squeeze has been completed, air under pressure is suppliedthrough the back blow inlet 12 to purge the slurry remaining in thepipings such as the inlet 9 and the like and further air under pressureis supplied through the feed blow inlet 1 l to dewater the filter cakes.

The cylinder 2 for clamping the filter plates are then released to openthe plates as shown in FIG. 2. At this time, the opening of thestationary filter plates 4 are effected by means of simultaneous filterplate open and close means according to the invention which will belater explained in detail. When the stationary filter plates 4 arebrought from a closed position as shown in FIG. 3 into an openedposition, the filter cloth 6 trained around the transfer rollers R and Rhaving the different diameters are inclined to relatively large angles,permitting the cakes to fall by gravity, which have attached to thatportions of the cloth advancing to the larger diameter rollers R thatis, the portions of the cloth on the left side of the respectivestationary filter plates 4 as viewed in FIG. 3. If the filter cloth isdriven while the filter plates are in the opened position, the scraperplates 17 shown in FIG. 2 serves to effect more full falls of the cakesby gravity so that they are completely removed from the cloth. Thetravelling cloth is cleaned by the cloth cleaning unit 16.

Referring to FIG. 4a, filter plate open and close means according to theinvention for use in a filter press having the hydraulic cylinder 2 forreciproc'ative movements of a loose head 18 supported on the side bar 1by rollers 19, comprises a motor 20 operative in synchronism with theextension and retraction of the hydraulic cylinder 2, feed screw shafts22 arranged along a frame of the press and rotated through bevel gears21A and 218 by the drive motor 20, and a link rail such for example as achannel shaped rail 24 as shown in FIG. 4b each end of which is securedto a nut 23 threadedly fitted with the feed screw shaft 22, on whichlink rail 24 are provided a plurality of rollers 25, each having acentral shaft to which are pivotted two links 26, the opposite ends ofwhich are pivotted to the loose head 18 and the filter plate 4,respectively, to form a serpentine link as a whole as shown in FIG. 4.

With such a construction of the filter plate open and close means,inasmuch as the bevel gears 21A and 218 have the same gear ratio, thefeed screw shafts 22 are rotated at the same speed to move the link rail24 in its horizontal state, thereby causing the serpentine link 26pivotally supported on the link rail 24 by the rollers 25 to extend orcontract with the vertical movement of the link rail 24 so that all ofthe filter plates are opened or closed simultaneously.

The effects of the filter plate open and close means according to theinvention are clearly evident as shown in FIGS. 5a and 5b. In the priorart as shown in FIG. 5a, filtering operations are intermittent owing tolong waste time which is indirect time such as for opening and closingthe filter plates except the time for filtering, and the averagefiltering rate v, as shown in broken line in FIG. 5a is much lower thanthat v of the present invention as shown in FIG. 5b wherein the wastetime has been shortened.

The operation of the filter press installing filter frames 5 through thefilter cloth 6 between the stationary filter plates 4 each enclosing themovable filter plate 3 and a diaphragm according to the invention willbe described with reference to FIG. 3. The slurry forced under pressurethrough slurry inlets 27 in the filter frames 5 is filtered through thefilter cloth 6, the filtrate being exhausted from filtrate outlets 29through filtrate collecting grooves 28 formed in the stationary filterplates 4, and the filtrate filtered through the opposite portion of thecloth being exhausted from drain holes 32 in the stationary filterplates through filtrate collecting grooves 30 formed in the movablefilter plates 3 and collecting holes 31 of the movable filter plates 3.Cakes remain in filter chambers A in the respective filter frames 5.

High pressure fluid is then forced into each pressure fluid chamber Bthrough a pressure fluid inlet 14 provided in each stationary filterplate 4 and communicating with the fluid chamber B, causing eachdiaphragm with the movable filter plate 3 to urge the cake in the filterchamber A to an extend corresponding to the thickness of the diaphragml5, and thereby each cake is further compressed to a lower watercontent. For that purpose, according to the invention the diaphragm ismade thicker at its main portion than at is periphery, which makes iteasy to mount the diaphragm on the plate 4 and makes the stroke of themovable plate longer, thereby making it possible to obtain cakes oflower water content than those in hitherto used filter presses.

In the present invention, a filter cake is retained attached to theportion of a filter cloth on the determined side of the same. In variousinvestigations, it has been found that if there is any difference infiltration resistance between opposite sides of a filter cloth, a cakeattaches without fail to the side where filtration resistance is largerthan that of the other side. In a preferred embodiment of the invention,the width of the filtrate collecting grooves in the form of ruggedshapes formed in a filter plate is purposely varied to cause adifference in filtration resistance, or wires are arranged between afilter plate and one of portions of the filter cloth forming one wall ofa filter chamber and between a filter plate and the other of theportions of the cloth and a filter plate forming the other wall of thechamber, and further a perforated plate is interposed between the wireand the portion of the cloth on either side of the filter chamber.

In the embodiment employing different width filtrate collecting groovesin the form of rugged shape formed in the filter plates, a filter plate3 adjacent to a filter cloth 6 arranged in a filter frame forming afilter chamber A is formed in its one surface with recesses 33 servingas collecting grooves for filtrate and with protrusions 34 serving toretain a cake in close contact with the cloth 6 enclosing the cake asshown in FIG. 6a. As the cloth 6 is brought into close contact with theprotrusions 34 of the filter plate 3, the filtration re sistance of thatportions of the cloth becomes larger. On the other hand, recesses andprotrusions in the filter plate 4 in opposition to the plate 3 are muchfewer than those in the plate 3 so that areas having higher filtrationresistance on the side of the plate 4 are wider than those on the sideof the plate 3. On opening the filter plates, the cake becomes out ofcontact with the cloth on the side of the plate 3 and is retainedattached to the cloth on the side of the plate 4 having a higherfiltration resistance as a whole.

In the embodiment employing a perforated plate, as shown in FIG. 6b,wires are arranged in contact with the filter plates on opposite sidesand further on one side between the wire 35 and the filter cloth isinterposed a perforated plate 36, the area of perforations of which haspreviously been adjusted, thereby causing a difference in filtrationresistance between the portions of the cloth on opposite sides andretaining the cake attached to the portion of the cloth on the side ofthe plate having the perforated plate.

In horizontal filter presses having endless filter cloths of the priorart, rollers for extending the cloth thereon, which are alternatelyarranged above and below filter frames and filter plates, have the samediameter.

Referring to FIG. 7, filter plates and frames are shown in broken lines,rollers in circles and a filter cloth in straight lines between therollers. Solid lines show a system of a prior filter press, dot-dashlines the diagrammatic arrangement of a filter cloth according to theinvention, and double dotted-dash lines the dia grammatic filter clothbringing about the same effect as in the present invention.

In FIG. 7, a contact length of a filter cloth with a roller is rm, towhich a travelling resistance is proportional, where a(radian) is acontact angle of the filter with the roller and r is the radius of theroller. If the upper roller having the radius r is modified to a rollerR having a smaller radius r a contact angle a at a larger diameterroller R decreases to a smaller angle y and also the contact angle a atthe smaller diameter roller R decreases to a smaller angle [3. Therollers R and R are alternately arranged above and below the filterframes and plates in a spaced relation by a distance L. In the case of ahitherto used filter press wherein all of rollers arranged on upper andlower portions of the press have the same diameter, a travellingresistance of a filter cloth is represented by 2p.r,a, where p. isresistance coefficient, whereas in the case of employing rollers, oneset of which rollers have the smaller radius r,., a travellingresistance is represented by p.(r,'y+r B). In comparison of the valuesof the resistances, p.(r y+r B) is less than 2pr a as can be seen fromthe above description and FIG. 7. On the other hand, if a contact anglewill be made smaller without changing a roller diameter, a pitch betweenrollers adjacent to each other one above the other must be enlarged from1 to 1 as shown in FIG. 7. As a result, a pitch between a filter frameand a filter plate as they are opened is also enlarged, so that theoverall length of the filter press is naturally lengthened, causing thecost of equipment to increase and giving rise to inconvenience inoperation.

To avoid this, in a filter press having a filter cloth extending betweenfilter frames and filter plates as shown in FIG. 3, the diameter of therollers R arranged above the filter frames 5 is made smaller than thatof the rollers R arranged below the filter plates 4 and the endlessfilter cloth is driven by means of cloth drive means provided at asuitable position on the filter press frame. In the filter press withsuch an arrangement, when the filter plates are in opened position onthe termination of a compression filtering and a squeeze process, thefilter cloth 6 extending between the rollers R and R arranged above thefilter frames 5 and below the filter plates 4 is inclined to a greaterextent (FIG. 7) than in prior art, permitting cakes attached to thecloth to more effectively fall by gravity and thereby making thetravelling resistance smaller than in the case of rollers having thesame diameter.

The filtration capacity of the filter press according to the inventionis of the order of 20 kgDS/m /hr which is remarkably greater than thatin hitherto used filter presses such as 2.5 kgDS/m /hr.

Moreover, the water content of the cake obtained by the filter pressaccording to the invention is of the order of 40 percent, which facultyis a significant advantage since hitherto used filter presses couldnever obtain cakes of less then 60 percent water content.

As above described, the filter press according to the inventionaccomplishes the dewatering of cake to the considerably much lower watercontent, the full automatic operation, the shortening of overall lengthof the press, the higher average filtering rate and the minimizedtravelling resistance of the filter cloth.

While several examples have been herein disclosed, it is obvious thatvarious changes can be made without departing from the spirit and scopeof the invention as set forth in the appended claims. Further, it is tobe understood that all matter hereinbefore set forth is to beinterpreted as illustrative and not in a limiting sense.

What is claimed is:

' l. A filter press for compression filtering and squeeze dewateringslurry through an endless filter cloth, comprising:

a plurality of transversely extending longitudinally spaced stationaryfilter plates;

a plurality of transversely extending longitudinally spaced movablefilter plates, each movable filter plate being alternately positionedbetween adjacent stationary filter plates;

a plurality of diaphragms each having a main portion which is thicker incross-section than its outer peripheral portions, each diaphragm havingits central portion connected to an associated movable filter and itsouter peripheral portion connected to an associated stationary filterplate so that the diaphragm is sandwiched therebetween;

the stationary filter plates each having a cavity formed therein forenclosing the diaphragm and movable filter plate, connected therewith;

a plurality of longitudinally spaced filter frames supported on a sidebar of the filter press, each frame being disposed between adjacentfaces of adjacent stationary and movable filter plates so as to form afilter chamber therebetween;

filter cloth disposed between the opposed sides of each filter frame andthe adjacent faces of the adjacent stationary and movable filter plates;

means for pressing the diaphragm and its attached movable filter platetoward the face of the adjacent stationary filter plate to compresstherebetween within the interposed filter frame between the filter cloththe slurry introduced into the filter chamber in the filter frame;

the faces of the movable and stationary filterplates being in contactwith the opposed sides of the filter frame through the filter cloth in amanner to provide a difference in filtration resistance between thefaces of the adjacent movable and stationary filter plates so that uponcompletion of the compressing action and the opening of the filterplates the cake of compressed slurry remaining is attached only to theportion of the filter cloth located on the side of the high filtrationresistance thereby facilitating the removing of the cake from the clothand dropping it out of the filter chamber upon the opening of the filterpress;

filter plate open and close means for opening and closing all of filterplates and filter frames simultaneously; and

filter cloth transfer means for shifting the filter cloth,

including transfer rollers consisting of a first set of rollers arrangedabove and a second set of rollers arranged below the filter plates andfilter frames the diameter of the first set of rollers being smallerthan that of the second set of rollers.

2. A filter plate for a filter press according to claim 1, wherein saiddifference in filtration resistance is obtained by difference in areasof collecting grooves forming filtrate paths through which the filtrateflows and which are formed in the opposed surface faces of said movableand stationary filter plates having interposed therebetween the filtercloth and filter frame.

3. A filter plate for a filter press according to claim 1, wherein saiddifference in filtration resistance is obtained by providing aperforated plate between the surface face of the movable filter plateand the adjacent filter cloth.

4. A filter plate for a filter press according to claim 1, wherein saiddifference in filtration resistance is obtained by providing aperforated plate between the sur face face of the stationary filterplate and the adjacent filter cloth.

5. A filter press for compression filtering and squeeze dewateringslurry through an endless filter cloth, comprising simultaneous filterplate open and close means including a drive motor operative insynchronism with the reciprocative speed of a hydraulic cylinder causingreciprocative movements of a loose head, and a plurality of rollers on alink rail secured to feed screw shafts driven by said drive motor, eachroller having a central shaft to which two link members are pivoted,opposite ends of which are in turn pivoted to said loose head and afilter plate, respectively, to form serpentine link means; diaphragmseach having a main portion to be secured to a movable filter plate beingmade thicker than its periphery to be secured to a stationary filterplate enclosing said movable filter plate and said diaphragm; filterframes supported on a side bar of the filter press and arranged betweenthe filter plates to form filter chambers, the faces of the movable andstationary filter plates being in contact with the respective sides ofthe filter frame through the filter cloth so as to provide a differencein filtration resistance between the faces of the movable and stationaryfilter plates, so that when the filter plates are opened the retainingcake of compressed slurry will be attached only to the portion of thefilter cloth on the side of high filtration resistance to facilitateremoving the cake from the cloth and dropping it out of the filterchamber; and filter cloth transfer means including transfer rollersconsisting of first and second sets of rollers arranged above and belowsaidfilter plates and filter frames, the diameter of said first rollersabove arranged being smaller than that of said second rollers.

6. A filter plate for a filter press according to claim 5, wherein saiddifference in filtration resistance is obtained by difference in areasof collecting grooves forming filtrate paths through which the filtrateflows and which are formed in the opposed surface faces of said movableand stationary filter plates having interposed therebetween the filtercloth and filter frame.

wherein said difference in filtration resistance is obtained byproviding a perforated plate between the surface face of the stationaryfilter plate and the adjacent filter cloth.

1. A filter press for compression filtering and squeeze dewateringslurry through an endless filter cloth, comprising: a plurality oftransversely extending longitudinally spaced stationary filter plates; aplurality of transversely extending longitudinally spaced movable filterplates, each movable filter plate being alternately positioned betweenadjacent stationary filter plates; a plurality of diaphragms eaCh havinga main portion which is thicker in cross-section than its outerperipheral portions, each diaphragm having its central portion connectedto an associated movable filter and its outer peripheral portionconnected to an associated stationary filter plate so that the diaphragmis sandwiched therebetween; the stationary filter plates each having acavity formed therein for enclosing the diaphragm and movable filterplate, connected therewith; a plurality of longitudinally spaced filterframes supported on a side bar of the filter press, each frame beingdisposed between adjacent faces of adjacent stationary and movablefilter plates so as to form a filter chamber therebetween; filter clothdisposed between the opposed sides of each filter frame and the adjacentfaces of the adjacent stationary and movable filter plates; means forpressing the diaphragm and its attached movable filter plate toward theface of the adjacent stationary filter plate to compress therebetweenwithin the interposed filter frame between the filter cloth the slurryintroduced into the filter chamber in the filter frame; the faces of themovable and stationary filterplates being in contact with the opposedsides of the filter frame through the filter cloth in a manner toprovide a difference in filtration resistance between the faces of theadjacent movable and stationary filter plates so that upon completion ofthe compressing action and the opening of the filter plates the cake ofcompressed slurry remaining is attached only to the portion of thefilter cloth located on the side of the high filtration resistancethereby facilitating the removing of the cake from the cloth anddropping it out of the filter chamber upon the opening of the filterpress; filter plate open and close means for opening and closing all offilter plates and filter frames simultaneously; and filter clothtransfer means for shifting the filter cloth, including transfer rollersconsisting of a first set of rollers arranged above and a second set ofrollers arranged below the filter plates and filter frames the diameterof the first set of rollers being smaller than that of the second set ofrollers.
 2. A filter plate for a filter press according to claim 1,wherein said difference in filtration resistance is obtained bydifference in areas of collecting grooves forming filtrate paths throughwhich the filtrate flows and which are formed in the opposed surfacefaces of said movable and stationary filter plates having interposedtherebetween the filter cloth and filter frame.
 3. A filter plate for afilter press according to claim 1, wherein said difference in filtrationresistance is obtained by providing a perforated plate between thesurface face of the movable filter plate and the adjacent filter cloth.4. A filter plate for a filter press according to claim 1, wherein saiddifference in filtration resistance is obtained by providing aperforated plate between the surface face of the stationary filter plateand the adjacent filter cloth.
 5. A filter press for compressionfiltering and squeeze dewatering slurry through an endless filter cloth,comprising simultaneous filter plate open and close means including adrive motor operative in synchronism with the reciprocative speed of ahydraulic cylinder causing reciprocative movements of a loose head, anda plurality of rollers on a link rail secured to feed screw shaftsdriven by said drive motor, each roller having a central shaft to whichtwo link members are pivoted, opposite ends of which are in turn pivotedto said loose head and a filter plate, respectively, to form serpentinelink means; diaphragms each having a main portion to be secured to amovable filter plate being made thicker than its periphery to be securedto a stationary filter plate enclosing said movable filter plate andsaid diaphragm; filter frames supported on a side bar of the filterpress and arranged between the filter plates to form filter chambers,thE faces of the movable and stationary filter plates being in contactwith the respective sides of the filter frame through the filter clothso as to provide a difference in filtration resistance between the facesof the movable and stationary filter plates, so that when the filterplates are opened the retaining cake of compressed slurry will beattached only to the portion of the filter cloth on the side of highfiltration resistance to facilitate removing the cake from the cloth anddropping it out of the filter chamber; and filter cloth transfer meansincluding transfer rollers consisting of first and second sets ofrollers arranged above and below said filter plates and filter frames,the diameter of said first rollers above arranged being smaller thanthat of said second rollers.
 6. A filter plate for a filter pressaccording to claim 5, wherein said difference in filtration resistanceis obtained by difference in areas of collecting grooves formingfiltrate paths through which the filtrate flows and which are formed inthe opposed surface faces of said movable and stationary filter plateshaving interposed therebetween the filter cloth and filter frame.
 7. Afilter plate for a filter press according to claim 5, wherein saiddifference in filtration resistance is obtained by providing aperforated plate between the surface face of the the movable filterplate and the adjacent filter cloth.
 8. A filter plate for a filterpress according to claim 5, wherein said difference in filtrationresistance is obtained by providing a perforated plate between thesurface face of the stationary filter plate and the adjacent filtercloth.